1. Field of the Invention
The present invention relates generally to the field of light-emitting diode (LED) technology. More particularly, the present invention relates to a high-brightness LED structure with overlapping first and second electrodes.
2. Description of the Prior Art
A light-emitting diode (LED) is a solid-state semiconductor light source, which is fabricated by semiconductor materials. LEDs are used in applications as diverse as replacements for aviation lighting, automotive lighting (particularly indicators) and in traffic signals. The compact size of LEDs has allowed new text and video displays and sensors to be developed, while their high switching rates are useful in advanced communications technology.
FIG. 1 is a plan view of a conventional light-emitting diode with comb-shaped electrodes. FIG. 2 is a cross-sectional view taken along line I-I′ of FIG. 1. As shown in FIG. 1 and FIG. 2, the conventional light-emitting diode 10 comprises a second electrode 30 disposed on the second semiconductor layer 20 and a first electrode 40 disposed on the first semiconductor layer 50. The second electrode 30 does not overlap with the first electrode 40. The first electrode 40 is formed in a comb-shaped trench 60 that is formed by etching through the second semiconductor layer 20 and the active layer 22. The trench 60 exposes a portion of the first semiconductor layer 50 and the first electrode 40 is disposed at the bottom of the trench 60.
As shown in FIG. 2, the second electrode 30 comprises a connecting portion 30a and a plurality of finger electrodes 30b orthogonally extending from the connecting portion 30a. The first electrode 40 comprises a connecting portion 40a and a plurality of finger electrodes 40b orthogonally extending from the connecting portion 40a. The connecting portion 30a is parallel with the connecting portion 40a. The finger electrodes 30b and the finger electrodes 40b are interdigitated in the area between the connecting portion 30a and the connecting portion 40a. In order to improve the current spreading characteristic of the LED device, the distance between the finger electrode 30b and the finger electrode 40b is remained fixed.
However, the above-described light-emitting diode has several drawbacks and shortcomings. For example, when the light-emitting diode 10 is in operation, the LED device is prone to local fracture or burn down due to point discharge that stems from the accumulation of the electric current at the tips of the finger electrodes 30b and the finger electrodes 40b. Further, the second electrode 30 on the second semiconductor layer 20 shades the light generated by the light-emitting diode 10 itself and affects the performance of the LED device.